We investigate ex-ante efficient contracts in an environment in which implementation is costless. In this environment, standard debt contracts will typically not be optimal. Optimal contracts may involve defaults, even in states in which the borrower is fully able to repay. We then examine the welfare costs of arbitrarily restricting the set of feasible contracts to standard debt contracts. When model parameters are calibrated to realistic values, the welfare loss from exogenously imposing this restriction is extremely small. Thus, if the implementation costs are actually nontrivial (as seems likely), standard debt contracts will be (very close to) optimal.

We consider a two country growth model with international capital markets. These markets fund capital investment in both countries, and operate subject to a costly state verification (CSV) problem. Investors in each country require some external finance, but also provide internal finance, which mitigates the CSV problem. When two identical (except for their initial capital stocks) economies are closed, they necessarily converge monotonically to the same steady state output level. Unrestricted international financial trade precludes otherwise identical economies from converging, and poor countries are necessarily net lenders to rich countries. Oscillation in real activity and international capital flows can occur.